[Python-Dev] sys.path[0]

[Guido van Rossum]

> Exactly for this reason, changing the working directory confuses
> inspect and pydoc and presumably anything else that tries to find
> source code.  There's no way to work around this because the true
> path information is simply not available, unless we fix the
> __file__ attribute.
> 
> I'd be in favour of setting all __file__ attributes to absolute paths.

Note that code objects have their own filename attribute, which is not
directly related to __file__, and that's the one that causes the most
problems.  I truly wish we could change marshal so that when it loads
a code object, it replaces the filename attribute with the filename
from which the object is loaded, but that's far from easy. :-(

> > > I'm disinclined to do anything about this, except perhaps warn that
> > > the script directory may be given as a relative path.
> 
> The current working directory is a piece of hidden global state.
> In general, hidden global state is bad, and this particular piece
> of state is especially important because it affects what Python
> modules get loaded.  I'd prefer for the interpreter to just set
> up sys.path correctly to begin with -- what's the point in doing
> it ambiguously only to fix it up later anyway?

Maybe things have changed, but in the past I've been bitten by
absolute path conversions.  E.g. I rememeber from my time at CWI that
automount caused really ugly long absulute paths that everybody
hated.  Also, there are conditions under which getcwd() can fail (when
an ancestor directory doesn't have enough permissions) so the code
doing so must be complex.

That said, I'd be +0 if someone gave me a patch that fixed the path of
the script (the only path that's not already absolutized by site.py).

--Guido van Rossum (home page: http://www.python.org/~guido/)